February 7 1964 - Signals from Space

Throughout the winter of 1963-64 Jupiter was a brilliant object, and provided observers with various surprises. Normally there are two distinct equatorial belts, but during this opposition the two belts seemed to combine, forming one equatorial' wedge' - an appearance also found in 1962-63.

Considerable attention was paid to the problem of the radio emissions from Jupiter, and a full-scale programme of study was initiated by the Florida State University team in collaboration with F. W. Hyde at St Osyth, near Clacton. In the programme of February 1964 the preliminary results were given, indicating that Hyde's own theory - that the emissions are basically solar — is likely to prove correct.

It had been intended to devote the whole programme to Jupiter, but in the event there were two spectacular developments in space research. The American rocket Ranger VI landed on the Moon, and there was also the launching of the balloon satellite Echo II. These could not be omitted, and so Hyde and I were joined in the studio by Howard Miles, who talked about Echo, and Peter Stewart, who discussed the reasons for the failure of the cameras carried in Ranger VI.

Spectacular advances in the space-research programme have been made during the first two months of 1964. In particular, the American rocket Ranger VI has hit the Moon. The vehicle was launched on January 29, and the landing was achieved at 9.24 on February 2, within fifteen miles of the planned position. The radio signals were still being received at Jodrell Bank up to the moment of impact, so that the timing is not in doubt; neither is there any question as to the landing site - Ranger VI, or its broken remains, now lies in the grey plain known as the Mare Tranquillitatis (Sea of Tranquillity), about thirty miles south of the well-marked crater Ross.

There are no reliable reports of any phenomena observed as the vehicle came down (a record of a minute flash about ninety seconds before impact was made at the Flagstaff Observatory in Arizona, but seems somewhat dubious). It is possible that a small crater has been produced, and it is also possible that the disturbance of the surface layers may have resulted in a visible patch, but the skies were uniformly cloudy until the Sun had already set over that part of the lunar surface.

Though the Americans achieved an important success with their guidance and launching techniques, the cameras on Ranger VI unfortunately failed to work, so that no pictures were received; it had been hoped to obtain views of the Moon from very close range. The vehicle had been equipped with a complicated switching mechanism actuated in three different ways, but all this was routed through one main switch - and this seems to have been the faulty component. A failure of this sort is doubly disappointing, but at least considerable progress has been made, and there is no reason to suppose that the next Ranger shot will be anything but successful.

A new balloon satellite, Echo II, has also been launched from the United States, and is the brightest artificial satellite so far sent up - much more conspicuous than the loo-foot balloon Echo I, which has been in orbit since August 1960. Echo II is 135 feet in diameter, and has a plastic skin only seven-tenths of a thousandth of an inch thick.

It has been put into a polar orbit (that is to say, it travels approximately over the north and south poles of the Earth), and when it next becomes well placed for observation in Britain, in a few weeks' time, it will be much too conspicuous, to be overlooked. Its purpose is to act as a reflector of radio waves, and messages will be sent from Russia to America by using Echo II. One great advantage of a 'passive satellite' of this kind is that extensive modifications of ground equipment do not involve modifications in the satellite itself; also, many stations, using many different frequencies, can use the satellite at the same time.

Mention should also be made of Elektron I and Elektron II, launched from Russia on 30 January; both came from one carrier rocket but have been put into very different orbits. They are not communications satellites, but are designed to send back informa­tion about the radiation zones surrounding the Earth. They will be easily observable, but will be comparatively faint, and by no means so conspicuous as Echo II even though they are much more elaborate.

Meanwhile, there have been developments in an entirely different sort of scientific programme - that of investigating the mysterious radio emissions from the planet Jupiter. Since the first positive results have now been obtained, it seems worth while to return to the subject.

Jupiter has been very conspicuous in the evening sky during the winter, and is still to be seen, though it now sets in mid-evening. On 28 February 1964 it will appear close to Venus, and the sight will be beautiful; the apparent distance between the two planets will be only 1 -y degrees, with Jupiter lying to the south. Needless to say, the two are not genuinely close together. Venus is a relatively small world, about the same size as the Earth and comparatively close; Jupiter is immense, since its equatorial diameter is over 88,000 miles, and is a very long way off, so that it is seen 'in the background'. The average distance between Jupiter and the Sun amounts to 483,000,000 miles.

Jupiter is a planet entirely different from the Earth. It is com­posed of gas, at least in its surface layers, and contains a great deal of hydrogen, together with hydrogen compounds such as ammonia and methane. There may be a solid, rocky core, overlaid by a thick layer of ice, as suggested by R. Wildt; it may be made up of gas all the way through, though the tremendous pressures deep below the surface would produce curious effects. In any case, it is extremely cold, and any form of life there is out of the question.

Normally, small telescopes will show well-defined cloud belts, together with other features such as spots. The Great Red Spot, which has been seen on and off for several centuries, may be regarded as semi-permanent, even though its exact nature is still obscure. During 1963 and early 1964 the telescopic aspect has been unusual; the equatorial belts seem to have merged, producing the appearance of a solid band across the planet's equator. The Red Spot has been decidedly prominent, and distinctly pinkish in hue.

It is nearly ten years since the American radio astronomers Burke and Franklin published their discovery of peculiar radia­tions from Jupiter. All the planets produce radio waves to some degree, and these may be used to determine the temperatures of the planets, but the radiations are all of very high frequency (and so of short wavelength). The radio waves from Jupiter proved to be comparatively long, and unlike any of those recorded from other planets. Moreover, they seemed to be spasmodic, so that they could not be predicted. The original discovery was accidental, and was unexpected, but there could be no doubt that Jupiter was in some way responsible.

The radiations from Jupiter may be converted to 'noise', sounding a little like the waves on seashore. They may also be recorded as a trace, using a pen-recorder, though great care has to be taken with identification in view of the fact that other types of interference produce traces which look almost exactly like emissions from Jupiter.

Naturally, attempts were at once made to determine the exact nature of the emissions. The first step was to see whether any visible features on Jupiter's disk could be positive emitters, and this was where the telescopic observers came in. Jupiter rotates very quickly (in less than ten hours), so the various features appear to be carried across the disk from one side to the other; shifts are noticeable even over periods of a few minutes. When a feature reaches the central meridian of Jupiter as seen from Earth, it is said to be in 'transit'. If the transits of various well-marked features coincided with radio bursts, it would be safe to assume that these features were in fact radio emitters.

Preliminary results were uncertain, but no definite correlations were established. During the present apparition of Jupiter (1963- 64), a concentrated programme has been started by C. H. Barrow and his team at Florida State University, working in conjunction with F. W. Hyde at his radio astronomy observatory at St Osyth, near Clacton in Essex. Jovian emissions have been recorded, and I have attempted to link these with my own visual observations of the planet, obtained with the telescopes at my observatory at East Grinstead in Sussex. It seems that there is no connection of any kind. Radio bursts do not occur at the moments when features such as the Red Spot and the curious white spots in Jupiter's south temperate zone come toward the central meridian; the radio emissions are independent of visual features. This negative result was generally expected, but is none the less decidedly significant.

Another interpretation is that the radio bursts are due to thunderstorms in the atmosphere of Jupiter. This, however, is now regarded as most unlikely. There are various objections: in particular, it seems that the power required would be so great, and cause so much disturbance, that effects would be visible telescopically. A third theory supposes that Jupiter's atmosphere focuses radio emissions coming from space and directs them toward the Earth, but here too there are serious objections. Also more or less abandoned is the idea that outbreaks occur on a solid surface far below Jupiter's outer gas, and so invisible.

A completely different view was put forward by Hyde some years ago. According to this, the radio emissions do not originate in Jupiter at all; they come basically from the Sun, so that we receive them second-hand and in somewhat modified form. Hyde points out that emissions from the Sun fall into three basic cate­gories. There are radio waves, which travel at the speed of light and which therefore reach the Earth in about eight-and-a-half minutes; there are fast particles, which reach us in about an hour; and there are tremendous bursts of particles and gas, which take between twenty and forty hours to travel from the Sun to the Earth. These latter bursts are sporadic, and are so violent that the effects must certainly reach out as far as Jupiter. Hyde supposes that the Jovian radio emissions are due to bursts from the Sun of this kind.

If Hyde's theory is correct, then outbursts on the Sun should be followed, after a set interval, by radio emissions from Jupiter; and it was to test the whole principle that the Florida-St Osyth programme was initiated in 1963. Continuous radio watch has been kept on Jupiter from both stations, while, of course, information about events on the Sun is easily obtained. Since solar disturbances affect magnetism, magnetic effects recorded on Earth are also taken into account. The programme is still going on, and final conclusions cannot yet be drawn, but everything points to the conclusion that Hyde is right; there is a definite correlation be­tween disturbances on the Sun and emissions from Jupiter. More­over, Jupiter seems to be less active, as a radio emitter, now that the 192 Sun is approaching its own minimum, so that violent solar out­bursts are less frequent.

If this effect is proved, it will be an important advance. In passing, it also provides a happy example of amateur-professional collaboration, since the Florida team is all-professional, whereas Hyde ranks as an amateur even though his observatory is elabor­ately equipped. The instruments in the two stations have been duplicated as closely as is possible, and special equipment has been sent from America to St Osyth.

Another experiment, this time a Russian one, has recently been made with pronounced success. For the first time, Jupiter has been contacted by radar. Basically, the principle of radar is to send out an energy pulse (which naturally travels at the same speed as light), bounce it off a solid object or the equivalent of a solid object, and then record the 'echo'. So far as the Moon is concerned, this was first done by the Hungarians and the Americans almost twenty years ago, and is not now regarded as in any way difficult. Radar echoes have been obtained from Venus, and have been used to refine the estimate of the astronomical unit or Earth-Sun distance; Mars has been contacted, and in 1963 the Russians were also able to obtain echoes from Mercury. Jupiter, however, is a much more difficult problem, simply because it is so remote.

The Russian work was carried out in September and October 1963, when the distance between Jupiter and the Earth was about 370,000,000 miles. Definite echoes were obtained, though they were of course very weak - in fact, the procedure was more or less equivalent to detecting a one-watt source at a distance of 370,000,000 miles. The total time-lapse between transmission and echo was sixty-six minutes. The success shows how rapidly Soviet scientists have advanced in this field. Obviously, the programme was not carried out merely as a curiosity. The Russians were anxious to study the reflective properties of Jupiter's surface, and also to gain information about the propagation of radio waves over very great distances. Full details are not yet available, but there can be no doubt that extremely useful advances have been made. In every way, then, Jupiter is an intriguing world. It is a spectacular object even in a small telescope, and it has been studied for several hundreds of years, but the new techniques have pro­duced results which are as fascinating as they are unexpected. Jupiter still holds many mysteries for us, and both visual and radio astronomers are working hard in an attempt to solve them.